1. Field of the Invention
The present invention relates to isolated polypeptides having alpha-glucuronidase activity and isolated polynucleotides encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the polynucleotides as well as methods of producing and using the polypeptides.
2. Background
Plant cell wall polysaccharides constitute 90% of the plant cell wall and can be divided into three groups: cellulose, hemicellulose, and pectin. Cellulose represents the major constituent of call wall polysaccharides. Hemicelluloses are the second most abundant constituent of plant cell walls. The major hemicellulose polymer is xylan. The structure of xylans found in cell walls of plants can differ significantly depending on their origin, but they always contain a beta-1,4-linked D-xylose backbone. The beta-1,4-linked D-xylose backbone can be substituted by various side groups, such as L-arabinose, D-galactose, acetyl, feruloyl, p-coumaroyl, and glucuronic acid residues.
Full hydrolysis of hemicellulose requires the action of a complex of enzymes including acetylxylan esterases, ferulic acid esterases, xylanases, arabinofuranosidases, xylosidases and alpha-glucuronidase. Alpha-glucuronidase is the enzyme that is responsible for hydrolysis of the alpha-1,2-glycosidic linkage between xylose and D-glucuronic acid or its 4-O-methyl ether.
It is an object of the present invention to provide novel polypeptides having alpha-glucuronidase activity suitable for use in industrial processes, e.g., in processes comprising conversion of cellulosic biomass into useful products including ethanol.
An alpha-glucuronidase from Aureobasidium pullulans being 67.3% identical has been disclosed by de Wet et al. (Enzyme Microb. Technol. 38:649-656, 2006).